Laboratory studies will be continued to evaluate further the safety of N. algerae to mammals. The immunity of mammals to N. algerae will be evaluated and an immunological diagnostic test for exposure to the microsporidan will be developed. Contingent on safety, field biological control tests will be undertaken against Anopheles stephensi in its natural setting (Pakistan). Field studies will be preceded by susceptibility testing of all commercially important invertebrates from the mosquito larval habitat. These studies will examine transmission, from generation to generation in the larval sites, the transmission of the parasite into new larval sites and all other invertebrates in the test sites will be examined for N. algerae infections. Along with the laboratory studies already completed, these data will provide an estimate of the effectiveness of N. algerae for control of a malaria vector mosquito. Since extensive safety testing for vertebrates and non-target invertebrates will be needed before widespread application in the field, this field test is needed in order to determine whether N. algerae will be effective enough as a biological control agent to warrant a long and expensive safety evaluation program.